Fourteen trials were included: nine RCTs in patients with congestive heart failure (n=274) and five RCTs in patients with COPD (n=91). COPD trials ranged from 6 to 8 points on the quality score; congestive heart failure trials ranged from 4 to 8 points. The most common methodological flaws were failure to conceal allocation and lack of blinding of patients, therapists and outcome assessors.
NMES in congestive heart failure:
Two trials compared NMES with usual care (n=56) but reported different primary outcomes. Across the two trials statistically significant improvements in the NMES condition were noted for peak workload and oxygen uptake, muscle strength and health status, and statistically significant decreases in fatigue.
Two trials compared NMES with sham stimulation (n=58) and both reported statistically significant improvements in health status, peak workload, oxygen uptake and six-minute walking distance.
Five trials compared NMES with endurance training (n=160) but reported only non-significant improvements for the NMES condition. The authors noted that three of these trials scored less than 6 our of 10 on the PEDro quality scale.
NMES in COPD:
One trial (n=15) compared NMES with usual care and reported statistically significant improvements in quadricep muscle function, exercise tolerance and health status.
Two trials (n=35) of NMES versus sham stimulation reported conflicting results. One study found no significant differences between interventions and the other reported statistically significant improvements on quadricep muscle strength and shuttle walk test. The authors noted that both trials scored 6 out of 10 on the PEDro quality scale.
One trial (n=24) compared NMES plus active limb mobilisation versus active limb mobilisation alone and found statistically significant improvements from baseline, but no significant differences between intervention groups.
One trial (n=17) compared NMES plus usual rehabilitation versus usual rehabilitation alone and found no difference in six-minute walking distance, but reported statistically significant benefits for the NMES plus rehabilitation group in quadriceps contraction and on the dyspnoea domain from a questionnaire.
Safety was not a predefined primary outcome in any of the trials; none of the studies reported any serious adverse events.